This invention relates to pipe preparing tools, and more particularly to a novel pipe preparing tool suitable for cutting, scoring or penetrating a surface of a plastics pipe.
Composite plastics pipes comprising an inner core and an outer protective layer are known. The outer protective layer may, for example, provide environmental protection, or protection against mechanical damage when the pipe is laid in a trench. In joining sections of such a pipe, it has been proposed to remove the outer protective layer in order to permit the installation of a pipe coupler, such as, for example, an electrofusion pipe coupler. Examples of such pipes with outer protective layers are described in WO-A-9300212, WO-A-9215818, European Patent Application No. 0474583 and in WO-A-9622485, the entire disclosures of which are incorporated herein by reference for all purposes.
In practice it has proved to be extremely difficult to remove the outer protective layer cleanly from the pipe inner core without damaging the inner core when using conventional tools such as knives, scrapers etc.
In GB1487033 there is described a tube cutting and chamfering tool comprising an adjustable C-shaped frame, a pair of spaced cutting wheels arranged in a common plane, supporting rollers for the tube, and a chamfering cutter adjustably located between the two cutting wheels. This tool is quite complex in design and is not readily adapted to remove the outer protective layer of a composite pipe.
GB1458366 describes a tool for cutting a cable sheath which comprises a loop-like frame, including at least two hingedly connected parts, means for releasably holding the frame parts in closed loop form, a handle connected to the frame, and a cutter assembly mounted for adjustment both inwardly and outwardly of the loop and angularly about the axis of its inward and outward movement. The cable sheath is supported by rollers mounted on the frame and, in some embodiments, also on the cutter assembly. This tool is complex both in design and operation.
U.S. Pat. No. 3,943,626 describes a pipe cutter adapted to be mounted on a chain pipe wrench. The pipe cutter comprises a cutter bit which projects adjustable beyond a rigid body member mounted on guide wheels.
GB2207377 describes a plastic pipe cutter which comprises a set of pipe grips and a cutting tool ring. The cutting tool ring comprises two half round steel bands which are hinged and have a fastening clamp. The cutting tool is housed in a rigid slotted boss.
GB2145647 describes a tool for removing a surplus bead of material from a pipe. The tool comprises a blade carried in a rigid blade holder formed in two half body portions carried on releasable clampling means comprising a pair of semi-circular steel straps.
In GB2296886 there is described and claimed a pipe preparing tool which comprises:                a frame having an opening adapted to receive a pipe or a portion thereof,        a first tapered roller means mounted transversely on the frame;        a second tapered roller means mounted transversely on the frame and spaced apart from the first tapered roller means;        the arrangement being such that the first and second tapered roller means have opposed directions of taper;        a cutting, scoring or penetrating means mounted on the frame and spaced apart from the first and second roller means; and        clamping means adapted to apply a clamping force to the pipe such that the first and second tapered roller means and the cutting, scoring or penetrating means are brought into contact with the pipe and the cutting, scoring or penetrating means penetrates a surface layer of the pipe;        the arrangement being such that the pipe and the tool can be rotated relatively to one another about the axis of the pipe whereby the cutting, scoring or penetrating means produces a helical groove in at least a surface layer of the pipe.        
This tool works well in practice, and can be used to strip off the outer layer of a composite pipe, but again some further simplification of the design would be desirable. In particular, it would be desirable to provide a cheaper tool and one wherein the number of moving parts, such as rollers, can be reduced.
The tools of the prior art, for example that of GB2296886, can only be used to cut the pipe circumferentially i.e. by rotating the tool about the longitudinal axis of the pipe. The need for cutting the pipe longitudinally i.e. parallel to the longitudinal axis of the pipe is therefore not met by the prior art devices.
Further problems associated with a prior art include the need to carefully select the depth to which cutting occurs so as not to damage the underlying pipe.
There is sometimes the need to provide differently-sized tools to cope with pipes of different diameters. For example, the tool of GB2296886 is limited in that it can only be used for pipes of small enough diameter to fit between the rollers 5–8 and the sliding arm 12 at its maximum setting. Some prior art tools cannot cater for pipes which are out of round, for example slightly oval as a result of storage in a coil.